Direct forward throw sweepers are well-known machines for sweeping debris from floors of buildings and also from outdoor areas. Such a sweeper uses a cylindrical brush rotating about a transverse horizontal axis to throw debris from a surface being swept directly into a debris hopper located in front of the brush. The hopper must, of course, have an opening facing the brush to permit entrance of the debris thrown by the brush.
When the sweeper has loaded as much debris as possible into the hopper then it must be emptied, or dumped. This involves raising the hopper a little if the debris is to be "low dumped" in a pile on the floor, or to a substantial height if the debris is to be "high dumped" into a truck body or trash container. Then the hopper is "rolled out" or tilted so the contained debris will slide out. Some sweepers are built to tilt forward and empty through a dump door in the front of the hopper, but a more economical design is to tilt the hopper to the rear and empty it through the opening that admits debris during sweeping, thereby saving the cost of a special dump opening and door. It is with the rear dump design that we are concerned.
High dumping a sweeper with a rear dump hopper involves raising the hopper and tilting it to the rear. Commonly these movements are combined by using a pair of lift arms attached at their forward ends to the sides of the hopper and pivoted at their rear ends on a transverse line at a high point on the sweeper. An actuator such as a hydraulic cylinder pivots the lift arms and attached hopper upwardly about the pivot point, so that in one motion the hopper opening rises to a desired height and also is turned to face downwardly. The machine is then moved forward so that the hopper is over the truck bed or trash container to be emptied into and the debris is dumped.
In order to prevent premature dumping of the debris while the hopper is being raised it is necessary that a door be provided to close the hopper opening until the hopper is in the final position where it is to be dumped. Such a door is commonly hinged across the top of the hopper opening so that it swings down to close the opening and is opened and closed by one or more actuators such as hydraulic cylinders which hold the door firmly in an open or closed position as selected by the machine operator. When the hopper has been tilted into final high dumping position its opening will be facing downward, and when the hopper door is opened it will project down and will be the lowest part of the hopper. As such it may be below the lip of the trash container being dumped into, and since it is positively connected to its actuator the machine is susceptible to damage if the operator backs it away from the container with the door open after dumping. Such misadventures are all too common.
Sweepers of the type being discussed commonly are equipped with a dust control system to prevent dust stirred up by the sweeping brush from escaping into the surrounding atmosphere. Such a dust control system commonly comprises a vacuum fan which pulls air in under the skirts that surround the brush, into the hopper, then through an air filter in a filter chamber adjacent to the hopper which removes entrained dust. Finally the clean air is exhausted to atmosphere.
In the past it has been common to further utilize the vacuum fan by offering a vacuum pickup wand with a flexible suction hose as an accessory for cleaning restricted areas where the sweeper could not enter. A means was provided for closing off the entrance to the air filter chamber, thereby converting it into an airtight plenum, and attaching the suction hose of the wand to a port in a side wall of this plenum, in a location on the so-called "dirty side" of the air filter.
This approach provided a functional vacuum cleaner, but it had a disadvantage in that debris picked up by the wand was fed into the filter chamber. This chamber was only intended to hold the fine dust typically collected by an air filter, and periodically to dump this dust, so a typical filter chamber commonly did not have much capacity or an adequate outlet to satisfactorily dump the sometimes rather coarse debris picked up by the wand. Such debris would on occasion clog the filter chamber and a very awkward service operation was required to clean it out. To date there has been no satisfactory solution to this problem.
Dust control is also a concern when dumping debris from the hopper of a sweeper, as well as when sweeping. The mass of debris being dumped generates an objectionable cloud of dust, which is aggravated in prior art sweepers by a stream of fine dust released from the filter chamber concurrently with the hopper dumping. A solution to this problem is needed, and even partial relief would be appreciated.
Also, it is advisable to thoroughly clean the bottom of the filter chamber periodically, but access to this area has been inconvenient and time consuming, a condition which needed improvement.